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Refactoring TypeScript

By : James Hickey

1 (1)

Refactoring TypeScript

1 (1)

By: James Hickey

Overview of this book

Refactoring improves your code without changing its behavior. With refactoring, the best approach is to apply small targeted changes to a codebase. Instead of doing a huge sweeping change to your code, refactoring is better as a long-term and continuous enterprise. Refactoring TypeScript explains how to spot bugs and remove them from your code. You’ll start by seeing how wordy conditionals, methods, and null checks make code unhealthy and unstable. Whether it is identifying messy nested conditionals or removing unnecessary methods, this book will show various techniques to avoid these pitfalls and write code that is easier to understand, maintain, and test. By the end of the book, you’ll have learned some of the main causes of unhealthy code, tips to identify them and techniques to address them.

Preface

Preface

About the Book

Free Chapter

1. Introduction

About TypeScript

What Is Refactoring?

Why Refactor at All?

When Should I Refactor?

2. Null Checks Everywhere!

Identification

Null Object Pattern

Special Case Pattern

3. Wordy Conditionals

Identification

Combining Conditionals

Extracting Methods from Conditionals

Extracting Conditional Logic to Explicit Classes

Pipe Classes

4. Nested Conditionals

Identification

Guard Clauses

Gate Classes

5. Primitive Overuse

Identification

Value Objects

Deceptive Booleans

6. Lengthy Method Signatures

Identification

Creating a Reusable Private Method

Extracting Data Objects

7. Methods That Never End

Identification

Give It a Name

Being Strategic

8. Dumping Grounds

Identification

One of These Things Is Not Like The Others

Speak or Listen

9. Messy Object Creation

Identification

Factory Functions

Combining Refactoring Techniques

10. Conclusion

This Is Just The Beginning!

Identification

One of the classic code smells is called primitive overuse.

It's deceptively simple.

Take this code, for example:

const email: string = user.email;
if(email !== null && email !== "") {
    // Do something with the email.
}

Notice that we are handling the email's raw data?

Or, consider this:

const firstname = user.firstname || "";
const lastname = user.lastname || "";
const fullName: string = firstname + " " + lastname;

Notice all that extra checking around making sure the user's names are not null? You've seen code like this, no doubt.

What's Wrong Here?

What's wrong with this code? There are a few things to think about:

That logic is not sharable and therefore will be duplicated all over the place.
In more complex scenarios, it's hard to see what the underlying business concept represents (which leads to code that's hard to understand).

CONTINUE READING

83

Tech Concepts

36

Programming languages

73

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